| 摘要 |
A selective nectar dispensing system for use with a bird feeder. The nectar dispensing system includes a pivot assembly which has a counterweight at one end and a feeding port restricting portion at another end. The pivot assembly is operable between a closed blocking position and an open feeding position. The counterweight normally biases the restricting portion to the closed blocking position and has a mass selected to both permit a feeding bird to move the restricting portion towards the open feeding position and to prevent movement of the restricting portion by an insect, thus providing selective access to the feeding port. The feeding port restricting portion is urged away from the feeding port against the force of the counterweight. Access to the feeding port is provided only when the feeding port restricting portion is urged away from the feeding port by the beak of a feeding bird in one embodiment and by the weight of the bird in another embodiment.
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